1. Field of the Invention
This invention relates to the field of electrotherapeutic methods, and more particularly to methods of treating infections through the use of electromagnetic waves.
2. Description of Related Art
When a person injures a bone so that an orthopedic surgeon is required to incise the person and place a mechanical device to stabilize the bone, most often the device that is placed is a metal alloy. This "implant" is used to strengthen the bone and hold it mechanically stable while the cells of the bone grow over the defect ("knit"). In some instances, the bone and "implant" will become infected.
Currently, the standard procedures for an infected implant are either re-incision of the patient and removal of the implant, or infusion of an antibiotic for a protracted period of time, with subsequent re-incision and removal of the implant if the infection persists. The first solution requires that the patient be taken to an operating suite, anesthesized with a general anesthetic, and then connected to monitors and support devices, such as an endotracheal tube placed to control his breathing, IV lines to administer fluids and blood, urinary catheters, etc. The new, sterile implant is placed immediately, exposing the affected area as filly as during the first operation and then physically removing the infected implant, irrigating the infected area, and then placing a new sterile implant.
In other situations, the surgeon may allow the patient to heal six weeks without the implant, and then re-incise the patient and re-introduce another implant During this six week period, the patient is usually treated with intravenous (V) antibiotics to try to kill the bacteria causing the infection.
In another method, a surgeon will elect to begin with a six week regimen of IV antibiotics, and if the medication does not work satisfactorily, or if the patient's condition deteriorates, then the surgeon will elect to remove the infected implant and replace it, as discussed above. Specific problems encountered during the above procedures include an increased risk of mortality (death) and morbidity (inability to function normally) for every instance that an individual has to undergo a major surgery in which he is placed under general anesthetic.
Furthermore, there is a significant cost borne by the patient in having a second major surgery. The cost includes the operating suite, surgeons time, the stand-by surgeon's time, the cost of a second implant, and the cost of the hospital stay after the operation to recuperate sufficiently to be discharged home.
Improvements to removal of the implant have been suggested. For example, U.S. Pat. No. 5,330,481, issued on Jul. 19, 1994 to Hood et al., teaches a method of using ultrasonic energy in the range of 20,000 to 40,000 Hertz (20 KHz-40 KHz) at from between 50 and 800 watts power for implantation or removal of an osteal prosthesis. However, that reference does not teach the sterilization of an implant without removing the implant from a human subject.
Methods of killing eukariotic cells, such as benign or malignant cancer cells, through sufficient heating with radio frequency (RF) energy have been proposed. For example, U.S. Pat. No. 5,928,217, issued on Jul. 27, 1999 to Mikus et al. discloses the use of a stent system for treatment of prostate tumors in which RF energy in an undisclosed frequency at from between 20 to 40 watts to raise the temperature of the stent to at least 40.degree. C. (104.degree. F.), and preferably 60.degree. C. (140.degree. F.) for between 10 and 40 minutes to destroy the eukariotic tumor cells. However, that reference does not disclose a method of killing prokaryotic cells through a standing wave of RF energy without decernable heating.